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He led the team to its first national girls secondary school title two years ago but reckons No2 is even more special.
St Hilda's beat Christchurch Girls' High School in a tense final on Wednesday.
A fine 80-run partnership between Olivia Gain (38) and Eden Carson (55 not out) set up the nine-run win.
"This is more special," Rosenburg said.
"This team does not have the same quality [of the 2016 team] and the level of the competition was equally good.
"But the girls just stepped up ... and everyone played together as a team fantastically."
The Sparks trio of Gain, Carson and Emma Black were the standout performers for St Hilda's but there were many gutsy contributions from all quarters, Rosenburg said.
"You can't win a cricket game with three or four stars, you have to have 11.
"The way the young girls integrated was just terrific."
Molly Loe, for example, strained a muscle early in a game and left the field in tears.
"But we put Voltaren on and strapped her up and she went out and bowled three at the death. That was big ticker stuff."
Rosenburg has been coaching the team for more than 20 years.
The school has been to the national finals for the past consecutive nine years.
"In the last five we've had three second-place finishes and two firsts, so I think consistently we'd be the best school in New Zealand.
"We have a school roll of 450 and a green-grassed area the size of a pocket handkerchief.
"To be fair I can't stop crying when I look at the pictures I'm flicking through on Facebook."